This invention relates to a vented fluid collection system having a blunt cannula and small collection chamber for use with an aspirator assembly.
It is often necessary to draw blood or fluid from a patient for diagnostic purposes. In fact, many times it is necessary to draw several samples of the blood from a patient within a relatively short span of time to monitor bodily functions and/or to monitor drug therapies. However, repetitive blood sampling may significantly reduce the patient's blood supply which may result in the patient becoming anemic and thus require a blood transfusion to replenish the his/her blood supply. Blood transfusion exposes the patient to the risk of exposure to hepatitis or HIV.
Laboratory blood analysis systems in existence today are capable of performing accurate diagnostic tests on blood samples of less than 1 ml in volume. However, typically, samples many times greater than that required are drawn from the patient. Therefore, a need exists for a reliable blood collection system having a small blood collection chamber capable of drawing a small sample of blood thereby decreasing the rate of a patient's blood depletion when numerous blood samples are drawn and yet capable of drawing a sufficient quantity for the testing required. Furthermore, unlike conventional needle syringes, it would be desirable to provide a blood collection system defining a small fixed volume so that a nurse or phlebotomist can not accidentally draw an excessive and unnecessarily large amount of blood.
Another problem that exists with conventional blood sampling techniques is that a standard syringe having a sharp needle is typically used. The sharp needle of the syringe is inserted either into a patient or an aspirator assembly that communicates with the patient's vascular system. However, on occasion, a nurse or a phlebotomist drawing the blood sample may stick him or herself with the sharp needle and thus expose him or herself to the patient's illness(es) or vice versa. Therefore, it would also be desirable for the blood collection system to have a blunt needle that can be inserted into an aspirator assembly during blood sampling. Blunt needles such as those described in my earlier U.S. application Ser. No. 07/935,907 can be employed in the blood collection system of this invention. Also, aspirator assemblies such as those disclosed in my earlier U.S. application Ser. No. 07/935,907 can be employed to cooperate with the blunt needle when blood is being drawn, to enable the blunt needle to communicate with the patient's vascular system.
Thus, it is an object of the present invention to provide a vented blood collection system comprising a blood collection device having a blunt tipped cannula coupled to a small fixed volume collection chamber.
In a first design of the blood collection device, the blunt tipped cannula is coupled to an adjoining small fixed volume collection chamber. To take a blood sample, the blunt cannula is inserted into an aspirator assembly which is in communication with the patient's vascular system. The patient's systemic blood pressure causes blood from the patient's vascular system to flow through the aspirator into a bore in the blunt cannula and further into the small collection chamber. Although no external pumping force is needed to siphon the blood from the patient's vascular system, such force may be applied if desired, for example, if the patient has particularly low blood pressure.
The end of the small collection chamber opposite to the cannula has an opening therein. A membrane is disposed in the opening in the collection chamber to allow air present in the small collection chamber to escape as blood enters the collection chamber through the cannula. However, this membrane does not permit the blood collected in the collection chamber to escape.
Alternatively, the opening can be covered by a removable cap which has a vented membrane incorporated therein. The cap can advantageously be removed to expose the end of the collection chamber and instruments can then be attached to the end of the collection chamber as necessary.
The blood collection device further comprises a cannula shroud which longitudinally surrounds the blunt cannula. Preferably, cannula cap is removably attached to the cannula shroud to cover the blunt cannula and thereby maintain a sterile environment therefor before the blood collection device is used, to protect the tip from unintentional contact, and to further prevent the blood sample in the collection chamber from exiting the collection chamber through the bore during subsequent transport to the lab.
In a second design of the blood collection device, a bore in the blunt tipped cannula acts as the small fixed volume collection chamber. The bore extends longitudinally through the blunt cannula from the distal blunt end to the opposite, proximal end.
As in the first design, the patient's systemic blood pressure causes blood from the patient's vascular system to flow through the aspirator into the bore in the blunt cannula. Depending on the dimensions of the bore, capillary flow plays a role in the collection of the blood sample. No external pumping force is needed to siphon the blood from the patient's vascular system, but such force may be applied if desired.
Desirably, a membrane as in the first design is disposed at the proximal end of the cannula bore to allow air present in the bore to escape as blood enters the bore as described above. This membrane does not permit the blood collected in the bore to escape.
The second design of the blood collection device may further comprise an enlarged housing longitudinally surrounding the blunt cannula to facilitate handling thereof. The enlarged housing may be injection molded about the blunt cannula or have an opening longitudinally therein into which the blunt cannula can be removably inserted.
The second design may be further modified to comprise a cannula shroud longitudinally surrounding the blunt cannula. The cannula shroud may be integral with the cannula or extend from an enlarged housing as described above. A cannula cap may be removably attached to the cannula and/or cannula shroud to cover the blunt cannula and thereby maintain a sterile environment therefor before the blood collection device is used, to protect the cannula tip from unintentional contact, and to further prevent the blood sample retained in the bore from exiting the bore when the blood collection device is subsequently transported.
As stated above, the aspirator assembly used with aspirator system can be similar to that described in U.S. application Ser. No. 07/935,907. The aspirator assembly comprises a casing including sleeves and an extension having an opening therein. Tubes are attached to the sleeves and one of the tubes is further coupled to a standard surgical needle or the like which is inverted into the patient to provide communication with the patient's vascular system. Alternately, a plug can be inserted into one of the cylindrical sleeves to block this sleeve.
A plug is inserted into the opening of the extension to prevent blood from escaping through this opening the aspirator assembly. The plug is comprised of a resilient material and has a perforation therein to allow insertion of the blunt cannula. When the cannula is absent from the perforation, the perforation is tightly closed to prevent leakage of fluid from the aspirator assembly.
The contour of the cannula tip and the tightness of the seal of the plug perforation are correlated. This correlation assures that the force needed to pass the blunt cannula tip into the perforation of the plug is considerably less than the force required to cause the tip of the blunt cannula to penetrate normal human skin. The perforation in the plug preferably allows the blunt cannula to initial penetration into the plug with a relatively small amount of force. The initial insertion of the blunt cannula holds the blunt cannula in alignment for further application of force to move the cannula tip into the aspirator assembly.
When the cannula is inserted into the aspirator assembly through the plug, the cannula extends into the portion of the aspirator assembly that communicates with the vascular system of the patient. Therefore, blood passes into the bore of the cannula and further into the small blood collection chamber of the blood collection device. In an alternative embodiment, the bore of the cannula acts as the collection chamber.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the appended claims.